This invention relates to cementing heads used for the introduction and separation of fluids in a well, such as the introduction and separation of a cement slurry. Specifically, the invention relates to plug containers, manifolds and quick-latch couplers. As is well known in the art, cementing plugs utilized to separate fluids passing through casing in a wellbore are often held in a plug container. Rather than opening the top of the casing to insert cementing plugs, a plug container is installed at the top of the casing. The plug container has flow lines attached thereto and may have a quick-latch coupler connected thereto, which can be utilized to attach the plug container to the casing. The plug container may also have a manifold attached thereto which directs fluid into the plug container. A typical prior art plug container is shown in Halliburton Sales & Service Catalog No. 39, page 3138. A typical manifold is shown in Halliburton Casing Sales Manual No. 820.00005, pg. 3-12. Prior art quick-latch couplers are shown in U.S. Pat. Nos. 4,524,998 and 4,613,161 assigned to the assignee herein, details of which are incorporated herein by reference.
At the beginning of a typical cementing job, the well casing and the well borehole are usually filled with drilling mud. To reduce the contamination at the interface between drilling mud and the cement which is pumped into the well casing on top of the drilling mud, a bottom cementing plug is often pumped ahead of the cement slurry so that the interface between the cement slurry and the drilling mud already in the well casing is defined by the bottom cementing plug.
As the cement is pumped into the well casing, the bottom cementing plug is pumped down the well casing. The bottom plug serves the function of wiping mud from the walls of the casing ahead of the cement slurry reducing dilution of the cement slurry, and serves to minimize contamination of cement as it is being pumped down the casing string. To separate the displacing fluid used to push the cement slurry out the tubular string and up the annular space, a top cementing plug is placed in line and pushed down the string by a displacing fluid. Typically, the bottom cementing plug is loaded into the plug container prior to pumping cement, and the top cementing plug will be loaded after the bottom plug is released. There may be times when only one cementing plug is used. In those cases, the plug is released after the cement to push the slurry out the tubular string. If well conditions dictate, a multiple plug container may be used which allows both cementing plugs to be released when desired without opening the plug container. Whether a single or multiple plug container is used, it can either be a free-fall or manifold type plug container.
The manifold utilized with plug containers is typically connected to inlets in the side of the plug container and is valved so that fluid can be displaced ahead of and behind cementing plugs. Often, the plug container and manifold may be made up as much as thirty feet off the rig floor. Because of the size, shape and weight of the plug and manifold assembly, it is difficult, time consuming and sometimes dangerous to make up the plug container, manifold and casing. Thus, there is a need for shorter and lighter plug containers, and more compact manifolds which are more maneuverable and easier and safer to handle.
Short plug container length is also important where rigs have short bales leaving little vertical distance above the top of the casing in which to make up the plug container. It is also desirable on some occasions to provide a means for quickly connecting the plug container to a casing collar in some manner other than making a threaded connection to a casing collar. Coupling apparatus for quick connection are shown in U.S. Pat. Nos. 4,613,161 and 4,524,998. While such apparatus work well, there is still a need for a shorter, more compact coupling apparatus that is easy to assemble. The present invention provides compact plug containers and manifolds which make assembly easier and make the cementing head easier to handle, and also provides a compact, readily assembled coupling apparatus.